Most sewing machines come with 3-5 sewing bobbins when buying. Many beginners assume that is enough bobbins. However, according to a sewing survey done in the US, on average sewers have between 20-30 sewing bobbins for each machine they own. You ALWAYS need more sewing bobbins!
Also not known, is that you must use the bobbins that are made for your machine. Although there are generic bobbins available, most bobbins are only compatible with its brand.
Some other useful facts are that plastic bobbins can bulge if filled with too much tension or too tightly wound. This might cause a mess in the bobbin area.
Should you swap plastic with metal bobbins or visa versa, remember to change your tension setting. Metal bobbins are heavier than plastic and the tension will change if you replace it with a different weight bobbin. If at all possible, refrain from swapping these two types.
One of regular problems we experience, is sewers who complains of incorrect stitching on their machine. On closer inspection, we find that the bobbin has been inserted incorrectly. The result is that it spins in the incorrect direction, giving poor quality stitching. Follow the picture on your machine which reminds you which way a bobbin should spin.
Be sure to cut this tail off so nothing sticks up. It might interfere with the forming and connecting of the top thread with the bobbin thread with every stitch made.